Cross-linkable compounds, optionally containing MQ silicon resins

ABSTRACT

The invention relates to new, cross-linkable compounds containing (A 1 ) linear organopolysiloxanes with aliphatically unsaturated hydrocarbon radicals, said organopolysiloxanes being of general formula (I) R 1   a R 3-a SiO(R 2 SiO) c [R 2 Si—Y—SiR 2 O(R 2 SiO) c ] d SiR 3-b R 1   b , wherein R can be the same or different, and represents a monovalent, optionally halogenated hydrocarbon radical which is free of terminal aliphatic carbon—carbon multiple bonds, R 1  represents a monovalent aliphatically unsaturated hydrocarbon radical, Y represents a bivalent organic radical which is free of terminal aliphatic carbon—carbon multiple bonds, a is 0 or 1, b is 0 or 1, and the sum of a+b per molecule is 1 or 2, c is a whole number to the value of 1 to 1000, d is 0 or a whole number to the value of 1 to 10, and optionally, (A 2 ) MQ silicone resins which are soluble in (A 1 ), on the condition that if MQ silicone resins (A 2 ) are not used, the sum of a+b in the formula (I) is 1.3 to 1.9 on average and that if MQ silicone resins (A 2 ) are used, the sum of a+b in formula (I) is 1.0 to 1.9 on average; (B) organo-silicon compounds with Si-bonded hydrogen atoms; (C) catalysts which promote the formation of an aliphatic multiple bond by Si-bonded hydrogen; and optionally, (D) agents which slow down the formation of an aliphatic multiple bond by Si-bonded hydrogen at room temperature.

The invention relates to crosslinkable compositions comprising

(A₁) organosilicon compounds containing aliphatically unsaturatedhydrocarbon radicals

and, if desired,

(A₂) MQ silicone resin,

(B) organosilicon compounds containing Si-bonded hydrogen atoms,

(C) catalysts which promote the addition of Si-bonded hydrogen ontoaliphatic multiple bond, and, if desired,

(D) agents which retard the addition of Si-bonded hydrogen ontoaliphatic multiple bond at room temperature

and to their use for producing coatings which repel tacky substances.

EP-B 403890 (Bayer A G; published on 16.03.1994) and the correspondingU.S. Pat. No. 5,077,369, and also EP-A 640662 (Bayer A G; laid open on01.03.1995) describe addition-crosslinking organopolysiloxane mixturesfor producing adhesion-reducing coatings. The organopolysiloxanespresent in the mixtures are branched, with the branching sitesrepresenting trifunctional monoorganosiloxy groups, so-called T units,and/or tetrafunctional siloxy groups, so-called Q units. In additionthey possess triorganosiloxy groups, so-called M units, as end groups,which contain at least one unsaturated hydrocarbon radical.

U.S. Pat. No. 5,082,915 (Shin-Etsu Chemical Company Ltd.; published on21.01.1992) describes paper-coating compositions which comprise abranched organopolysiloxane having at least two Si-bonded alkenyl groupsand at least one SiC-bonded siloxane side chain of the formula—(CH₂)_(m)(R¹ ₂SiO)_(n)—SiR¹ ₃ per molecule, where R¹ is a monovalenthydrocarbon radical, preferably a methyl radical, m is an integer from 2to 8 and n is an integer from 5 to 100.

EP-A 761 790 (Dow Corning Corporation; laid open on Mar. 12, 1997)discloses crosslinkable silicone coating compositions which compriseorganopolysiloxanes having Si-bonded vinyl groups or higher alkenylgroups and SiC-bonded groups of the formula —(CH₂)_(n)Si(OR)₃ (where Ris a monovalent hydrocarbon radical and n is an integer from 2 to 20).

The use of MQ silicone resins as agents for adjusting the release forcein coating compositions is known from U.S. Pat. No. 4,123,604 (DowCorning Corporation; published on Oct. 31, 1978), EP-B 535 687(Wacker-Chemie GmbH; published on Jun. 15, 1994) and EP-B 607 869(Wacker-Chemie GmbH; published on Apr. 5, 1995).

The object was to provide novel compositions based on organosiliconcompounds which crosslink in the presence of catalysts by the additionof Si-bonded hydrogen onto aliphatic multiple bond. A further object wasto provide novel compositions for the production of coatings which repeltacky substances. Yet another object was to provide abhesive coatingcompositions which give abrasion-resistant coatings, i.e. which adhereto the substrate such that they cannot be separated by mechanicalinfluences, for example by rubbing, from the substrate, so that they donot become partly detached when carriers located on them and providedwith adhesive, such as labels, are peeled off, which would otherwisereduce the bonding strength of the labels. A further object was toprovide abhesive coating compositions which give tack-free well-curedcoatings. These objects are achieved by the invention.

The invention provides crosslinkable compositions comprising

(A₁) linear organopolysiloxanes containing aliphatically unsaturatedhydrocarbon radicals, of the general formula

R¹ _(a)R_(3-a)SiO(R₂SiO)_(c)[R₂Si—Y—SiR₂O(R₂SiO)_(c)]_(d)SiR_(3-b)R¹_(b)  (I)

where R can be identical or different and is a monovalent, unsubstitutedor halogenated hydrocarbon radical which has from 1 to 18 carbon atomsper radical and is free from terminal aliphatic carbon—carbon multiplebonds,

R¹ is a monovalent aliphatically unsaturated hydrocarbon radical havingfrom 2 to 14 carbon atoms per radical,

Y is a divalent organic radical which is free from terminal aliphaticcarbon—carbon multiple bonds,

a is 0 or 1,

b is 0 or 1,

and the sum a+b per molecule is 1 or 2,

c is an integer from 1 to 1000 and

d is 0 or an integer from 1 to 10,

and, if desired,

(A₂) MQ silicone resins which are soluble in (A₁), with the proviso thatwithout the use of MQ silicone resins (A₂) the sum a+b in formula (I) ison average from 1.3 to 1.9, and that with the use of MQ silicone resins(A₂) the sum a+b in formula (I) is on average from 1.0 to 1.9,

(B) organosilicon compounds containing Si-bonded hydrogen atoms,

(C) catalysts which promote the addition of Si-bonded hydrogen ontoaliphatic multiple bond,

and, if desired,

(D) agents which retard the addition of Si-bonded hydrogen ontoaliphatic multiple bond at room temperature.

The invention also provides a process for producing coatings which repeltacky substances, by applying crosslinkable compositions comprising

(A₁) linear organopolysiloxanes containing aliphatically unsaturatedhydrocarbon radicals, of the general formula

R¹ _(a)R_(3-a)SiO(R₂SiO)_(c)[R₂Si—Y—SiR₂O(R₂SiO)_(c)]_(d)SiR_(3-b)R¹_(b)  (I)

where R, R¹, Y, a, b, c and d have the meaning indicated above for them,

and, if desired,

(A₂) MQ silicone resins which are soluble in (A₁),

with the proviso that

without the use of MQ silicone resins (A₂) the sum a+b in formula (I) ison average from 1.3 to 1.9, and that with the use of MQ silicone resins(A₂) the sum a+b in formula (I) is on average from 1.0 to 1.9,

(B) organosilicon compounds containing Si-bonded hydrogen atoms,

(C) catalysts which promote the addition of Si-bonded hydrogen ontoaliphatic multiple bond,

and, if desired,

(D) agents which retard the addition of Si-bonded hydrogen ontoaliphatic multiple bond at room temperature

to the surfaces which are to be made repellent to tacky substances andsubsequently curing the crosslinkable composition.

The linear organopolysiloxanes (A₁) according to the invention,containing aliphatically unsaturated hydrocarbon radicals, preferablypossess a viscosity of from 5 to 20,000 mm²/s at 25° C., preferably from20 to 1000 mm²/s at 25° C. and, with particular preference, from 20 to500 mm²/s at 25° C.

The organopolysiloxanes according to the invention preferably haveiodine numbers of between 1 and 80, preferably between 4 and 15, theiodine number indicating the amount of iodine, in grams, consumed in thecourse of addition onto the double bond, per 100 rams oforganopolysiloxane of the invention that is employed.

Examples of radicals R are alkyl radicals, such as the methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl,neopentyl and the tert-pentyl radical, hexyl radicals, such as then-hexyl radical, heptyl radicals, such as the n-heptyl radical, octylradicals, such as the n-octyl radical and isooctyl radicals such as the2,2,4-trimethylpentyl and the 2-ethylhexyl radical, nonyl radicals, suchas the n-nonyl radical, decyl radicals, such as the n-decyl radical,dodecyl radicals, such as the n-dodecyl radical, tetradecyl radicals,such as the n-tetradecyl radical, hexadecyl radicals, such as then-hexadecyl radical, and octadecyl radicals, such the n-octadecylradical, cycloalkyl radicals, such as the cyclopentyl, cyclohexyl and4-ethylcyclohexyl radical, cycloheptyl radicals, norbornyl radicals andmethylcyclohexyl radicals, aryl radicals, such as the phenyl,biphenylyl, naphthyl and anthryl and phenanthryl radicals; alkarylradicals, such as o-, m-, p-tolyl radicals, xylyl radicals andethylphenyl radicals aralkyl radicals, such as the benzyl radical, andalso the α- and the β-phenylethyl radical.

The radical R is preferably the methyl radical.

Examples of halogenated radicals R are haloalkyl radicals, such as the3,3,3-trifluoro-n-propyl radical, the 2,2,2,2′,2′,2′-hexafluoroisopropylradical and the heptafluoroisopropyl radical, and haloaryl radicals,such as the o-, m- and p-chlorophenyl radicals.

Y is preferably a divalent hydrocarbon radical which can contain one ormore separate oxygen atoms.

Examples of radicals Y are those of the formula —CH₂CH₂—, —CH(CH₃)—,—(CH₂)₄—, —(CH₂)₅—, —(CH₂)₆—, —(CH₂)₈—, —(CH₂)₁₀—, —(CH₂)₁₂—,—(CH₂)₃O(CH₂)₃—, 1,3-(CH₂CH₂)₂ (C₆H₄), 1,4-(CH₂CH₂)₂(C₆H₄),1,3-(CH₂CHCH₃)₂(C₆H₄), preference being given to the radicals of theformula —CH₂CH₂—, —CH(CH₃)—, —(CH₂)₆—, —(CH₂)₈— and particularpreference being given to the radical of the formula —CH₂CH₂—.

The radicals R¹ preferably have a terminal double bond. Examples ofradicals R¹ are the vinyl, allyl, 3-butenyl, 5-hexenyl, 7-octenyl,9-decenyl, 11-dodecenyl, 3-allyloxypropyl, 2-(3-vinylphenyl)ethyl andthe 2-(4-vinylphenyl)ethyl radical, preference being given to the vinyland the 5-hexenyl radical and particular preference to the vinylradical.

If MQ silicone resins (A₂) are not used, the organopolysiloxanes (A₁)have as end groups on average from 65 to 95 mol-%. of radicals R¹,preferably ω-alkenyl end groups (or as end groups from 35 to 5 mol-% ofradicals R, preferably methyl end groups), corresponding to an averagesum a+b of from 1.3 to 1.9. The sum a+b is preferably on average from1.3 to 1.8.

If MQ silicone resins (A₂) are used, the organopolysiloxanes (A₁) haveas end groups on average from 50 to 95 mol-% of radicals R¹, preferablyω-alkenyl end groups (or as end groups from 50 to 5 mol-% of radicals R,preferably methyl end groups), corresponding to an average sum a+b offrom 1.0 to 1.9. The sum a+b is preferably on average from 1.0 to 1.5,in particular from 1.1 to 1.4.

With the compositions according to the invention it is preferred toemploy a mixture of different organopolysiloxanes (A₁). c is preferablyan integer from 10 to 300, preferably from 20 to 150.

d is preferably 0 or an integer from 1 to 3; preferably, d is 0.

Processes for preparing linear organopolysiloxanes of the formula (I)where d is 0 are known to the skilled worker. A preferred process is theacid-catalysed equilibration of polydialkylsiloxanes having alkyl endgroups with polydialkylsiloxanes having ω-alkenyl end groups.

Linear organopolysiloxanes of the formula (I) where d is an integer from1 to 10 and processes for their preparation are described in U.S. Pat.No. 5,057,549 and in the corresponding DE-A 39 14 896.

MQ silicone resins (A₂), which are used if desired, are those comprisingunits of the general formula

R₃SiO_(½)(IV), R¹R₂SiO_(½)(V) and SiO₂(VI),

where R and R¹ have the meaning indicated above for them.

The ratio of M units of the formula (IV) and (V) to Q units of theformula (VI) is preferably from 0.5 to 1.5, more preferably from 0.5 to1.0. The ratio of saturated M units of the formula (IV) to unsaturated Munits of the formula (V) is preferably from 5 to 20, more preferablyfrom 5 to 10.

The MQ silicone resins may include small amounts of T units of theformula RSiO_(3/2) and D units of the formula R₂SiO.

Processes for preparing the MQ silicone resins (A₂) are described inEP-B 535 687, which was mentioned at the outset, and is incorporatedherein by reference.

If MQ silicone resins (A₂) are used, the MQ silicone resins (A₂) areemployed in amounts of preferably from 40 to 60% by weight, morepreferably from 50 to 55% by weight, based in each case on the overallweight of the constituents (A₁) and (A₂).

High concentrations of MQ silicone resin lead to greatly increasedviscosities, so that when using more than 60% by weight of MQ siliconeresin (A₂) it is normally no longer possible to do without the additionof solvent.

The use of MQ silicone resins (A₂) has the advantage that it is possibleto adjust the release force of the abhesive coatings.

In the case of the crosslinkable compositions according to the inventionas well it is possible as constituent (B) to use the sameorganopolysiloxanes, containing Si-bonded hydrogen atoms, which it hasbeen possible to employ in the case of all hitherto known compositionscomprising organopolysiloxanes containing aliphatically unsaturatedhydrocarbon radicals, such as vinyl groups, organopolysiloxanescontaining Si-bonded hydrogen atoms, and catalysts which promote theaddition of Si-bonded hydrogen onto aliphatic multiple bond.

The organopolysiloxanes (B) preferably contain at least 3 Si-bondedhydrogen atoms.

As constituent (B) it is preferred to use organopolysiloxanes comprisingunits of the formula: $\begin{matrix}\begin{matrix}{H_{e}R_{f}{SiO}_{\frac{4 - {({e + f})}}{2}}} & \square\end{matrix}_{\square} & ({II})\end{matrix}$

where R has the meaning indicated above for it,

e is O or 1,

f is 0, 1, 2 or 3 and

the sum e+f is not greater than 3,

more preferably those of the formula

H_(g)R_(3-g)SiO(SiR₂O)_(k)(SiRHO)_(l)SiR_(3-g)H_(g)  (III)

where R has the meaning indicated above for it,

g is 0 or 1,

k is 0 or an integer from 1 to 100 and

l is 0 or an integer from 1 to 100,

or organosilicon compounds containing Si-bonded hydrogen atoms asdescribed in the German application with the file reference 196 02 663.6of the Applicant, or mixtures of the above-mentioned organopolysiloxanesand organosilicon compounds.

Examples of organopolysiloxanes (B) are, in particular, copolymerscomprising dimethylhydridosiloxane, methylhydridosiloxane,dimethylsiloxane and trimethylsiloxane units, copolymers comprisingtrimethylsiloxane, dimethylhydridosiloxane and methylhydridosiloxaneunits, copolymers comprising trimethylsiloxane, dimethylsiloxane andmethylhydridosiloxane units, copolymers comprising methylhydridosiloxaneand trimethylsiloxane units, copolymers comprisingmethylhydridosiloxane, diphenylsiloxane and trimethylsiloxane units,copolymers comprising methylhydridosiloxane, dimethylhydridosiloxane anddiphenylsiloxane units, copolymers comprising methylhydridosiloxane,phenylmethylsiloxane, trimethylsiloxane and/or dimethylhydridosiloxaneunits, copolymers comprising methylhydridosiloxane, dimethylsiloxane,diphenylsiloxane, trimethylsiloxane and/or dimethylhydridosiloxane unitsand copolymers comprising dimethylhydridosiloxane, trimethylsiloxane,phenylhydridosiloxane, dimethylsiloxane and/or phenylmethylsiloxaneunits.

Processes for preparing organopolysiloxanes (B), including thoseorganopolysiloxanes (B) of the preferred kind, are generally known.

Organosilicon compounds (B) are preferably employed in amounts of from0.5 to 6, preferably from 1 to 3, and, with particular preference, from1.2 to 2.5 gramme atoms of Si-bonded hydrogen per mole of radical R¹ inthe organopolysiloxanes (A) containing aliphatically unsaturatedhydrocarbon radicals.

As catalysts (C) which promote the addition of Si-bonded hydrogen ontoaliphatic multiple bond it is also possible in the case of thecompositions according to the invention to use the same catalysts whichit has also been possible to employ to promote crosslinking in the caseof the hitherto known compositions for crosslinking organosiliconcompounds containing aliphatic multiple bonds with compounds containingSi-bonded hydrogen. The catalysts (C) preferably comprise a metal fromthe group of the platinum metals or a compound or a complex from thegroup of the platinum metals. Examples of such catalysts are metallicand finely divided platinum, which can be on carriers such as silica,alumina or active charcoal, compounds or complexes of platinum, such asplatinum halides, e.g. PtCl₄, H₂PtCl₆*6H₂O, Na₂PtCl₄*4H₂O,platinum-olefin complexes, platinum-alcohol complexes,platinum-alcoholate complexes, platinum-ether complexes,platinum-aldehyde complexes, platinum-ketone complexes, includingreaction products of H₂PtCl₆*6H₂O and cyclohexanone,platinum-vinylsiloxane complexes, such asplatinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes with orwithout a content of detectable inorganically bonded halogen,bis(gammapicoline)platinum dichloride, trimethylenedipyridineplatinumdichloride, dicyclopentadieneplatinum dichloride, dimethylsulphoxide-ethyleneplatinum(II) dichloride, cyclooctadieneplatinumdichloride, norbornadieneplatinum dichloride, gamma-picolineplatinumdichloride, cyclopentadieneplatinum dichloride, and reaction products ofplatinum tetrachloride with olefin and primary amine or secondary amineor primary and secondary amine in accordance with U.S. Pat. No.4,292,434, such as the reaction product of platinum tetrachloride,dissolved in 1-octene, with sec-butylamine, or ammonium-platinumcomplexes in accordance with EP-B 110 370.

Catalyst (C) is preferably employed in amounts of from 5 to 500 ppm byweight (parts by weight per million parts by weight), in particular from10 to 200 ppm by weight, calculated in each case as elemental platinummetal and based on the overall weight of the organopolysiloxanes (A) and(B).

As agents which retard the addition of Si-bonded hydrogen onto aliphaticmultiple bond at room temperature, so-called inhibitors (D), it is alsopossible in the case of the compositions according to the invention touse, if desired, all inhibitors which it has also been possible to useto date for the same purpose. Examples of inhibitors are1,3-divinyl-1,1,3,3-tetramethyldisiloxane, benzotriazole,dialkylformamides, alkylthioureas, methyl ethyl ketoxime, organic ororganosilicon compounds having a boiling point of at least 25° C. at1012 mbar (abs.) and at least one aliphatic triple bond in accordancewith U.S. Pat. No. 3,445,420, such as 1-ethynylcyclohexan-1-ol,2-methyl-3-butyn-2-ol, 3-methyl-1-pentyn-3-ol,2,5-dimethyl-3-hexyne-2,5-diol and 3,5-dimethyl-1-hexyn-3-ol,3,7-dimethyl-oct-1-yn-6-en-3-ol, inhibitors in accordance with U.S. Pat.No. 2,476,166, such as a mixture of diallyl maleate and vinyl acetate,and inhibitors in accordance with U.S. Pat. No. 4,504,645, such asmaleic monoesters.

The inhibitor (D) is preferably employed in amounts of from 0.001 to 10%by weight, based on the overall weight of the organopolysiloxanes (A)and (B).

Examples of further constituents which can be used in connection withthe compositions according to the invention are solvents, adhesionpromoters and pigments.

The solvents used if desired in connection with the compositionsaccording to the invention can be the same solvents which it has beenpossible to use in connection with the hitherto known compositionscomprising organopolysiloxanes containing aliphatically unsaturatedhydrocarbon radicals, organopolysiloxanes containing Si-bonded hydrogen,and catalysts which promote the addition of Si-bonded hydrogen ontoaliphatic double bond. Examples of such solvents are petroleum spirits,for example alkane mixtures having a boiling range from 80° C. to 110°C. at 1012 mbar (abs.), n-heptane, benzene, toluene and xylenes,halogenated alkanes having from 1 to 6 carbon atoms, such as methylenechloride, trichloroethylene and perchloroethylene, ethers, such asdi-n-butyl ether, esters, such as ethyl acetate, and ketones, such asmethyl ethyl ketone and cyclohexanone.

If organic solvents are used they are judiciously employed in amounts offrom 10 to 95% by weight, based on the overall weight of theorganopolysiloxanes (A) containing aliphatically unsaturated hydrocarbonradicals.

The sequence when mixing the constituents (A), (B), (C) and, if used,(D) is not actually critical, although for practical purposes it hasbeen found appropriate to add the constituent (C), i.e. the catalyst,last to the mixture of the other constituents.

The crosslinking of the compositions according to the invention takesplace preferably at from 50 to 150° C., preferably at from 80 to 150° C.Energy sources used for crosslinking by heating are preferably ovens,for example convection drying ovens, heating tunnels, heated rollers,heated plates or heat rays in the infrared range.

Besides exposure to heat, the compositions of the invention can also becrosslinked by irradiation with ultraviolet light or by irradiation withUW and IR light. The ultraviolet light used is customarily that having awavelength of 253.7 nm. In commerce there are a large number of lampswhich emit ultraviolet light with a wavelength of from 200 to 400 nm,and which preferentially emit ultraviolet light with a wavelength of253.7 mm.

The compositions according to the invention have the advantage thatafter crosslinking they give coatings which are resistant to abrasion.In addition, tack-free and well-cured coatings are obtained, so thatthere is virtually no adverse effect on the bonding strength of theadhesives which come into contact with the coatings.

The application of the compositions according to the invention to thesurfaces to be made repellent to tacky substances can be accomplished inany desired manner which is suitable and widely known for the productionof coatings from liquid substances, for example by dipping, brushing,pouring, spraying, rolling, printing, for example by means of an offsetgravure coating device, by knife coating, or by means of an airbrush.

The surfaces which are to be made repellent to tacky substances andwhich can be treated in the context of the invention can comprisesurfaces of any desired materials which are solid at room temperatureand 1012 mbar (abs.). Examples of such surfaces are those of paper,wood, cork and polymer films, for example polyethylene films orpolypropylene films, woven and nonwoven fabric of natural or syntheticfibres or glass fibres, ceramic articles, glass, metals,polyethylene-coated paper, and boards, including that of asbestos. Theabove-mentioned polyethylene can in each case comprise high-pressure,medium-pressure or low-pressure polyethylene. The paper can compriselow-grade paper types, such as absorbent papers, including kraft paperwhich is raw, i.e. has not been pretreated with chemicals and/orpolymeric natural substances, having a weight of from 60 to 150 g/m²,unsized papers, papers of low freeness value, mechanical papers,unglazed or uncalendered papers, papers which are smooth on one sideowing to the use of a dry glazing cylinder during their production,without additional complex measures, and are therefore referred to as“machine-glazed papers”, uncoated papers or papers produced from wastepaper, i.e. so-called recycled papers. The paper to be treated inaccordance with the invention can also, however, of course comprisehigh-grade papers, such as low-absorbency papers, sized papers, papersof high freeness value, chemical papers, calendered or glazed papers,glassine papers, parchmentized papers or precoated papers. The boardsmay also be of low or high grade.

The compositions according to the invention are suitable, for example,for the production of release, backing and interleaving papers,including interleaving papers which are employed in the production of,for example, cast films or decorative films, or of foams, includingthose of polyurethane. The compositions according to the invention arealso suitable, for example, for the production of release, backing andinterleaving cards, films and cloths, for treating the reverse sides ofself-adhesive tapes or self-adhesive films or the written faces ofself-adhesive labels. The compositions according to the invention areadditionally suitable for treating packing material, such as thatcomprising paper, cardboard boxes, metal foils and drums, for example,cardboard, plastic, wood or iron, which is or are intended for thestorage and/or transportation of tacky goods, such as adhesives, stickyfoodstuffs, for example cakes, honey, sweets and meat, bitumen, asphalt,greased materials and crude rubber. A further example of the use of thecompositions according to the invention is the treatment of backings forthe transfer of pressure-sensitive adhesive layers in the so-calledtransfer process.

The compositions according to the invention are suitable for theproduction of the self-adhesive materials joined to the release paper,both by the off-line method and by the in-line method. In the off-linemethod, the silicone composition is applied to the paper and crosslinkedand then, in a subsequent step, normally after the winding-up of therelease paper onto a roll and after storage of the roll, an adhesivefilm, which lies for example on a label face paper, is applied to thecoated paper and the assembly is then pressed together. In the in-linemethod, the silicone composition is applied to the paper andcrosslinked, the silicone coating is coated with the adhesive, the labelface paper is then applied to the adhesive, and finally the assembly ispressed together.

Preparing the Organopolysiloxanes (A):

Polymer I:

A mixture of 1200 g of an α, ω-divinylpolydimethylsiloxane having aviscosity of 217 mm²/s at 25° C. and 100 g of a methyl-terminatedpolydimethylsiloxane having a viscosity of 346 mm²/s at 25° C. isequilibrated to constant viscosity with 50 ppm of phosphonitrilicchloride at 125° C. The catalyst is neutralized, and the crude productis filtered and freed from volatile by-products at 160° C. and 3 hPa.This gives a clear oil having a viscosity of 180 mm²/s at 25° C. and aniodine number of 6.9. The product contains on average 94 mol-% of vinylend groups (a+b=1.88).

Polymer II:

Analogous repetition of Example 1 with only 700 g of theα,ω-divinylpolydimethylsiloxane gives a polymer having a viscosity of204 mm²/s at 25° C. and an iodine number of 6.7. The product contains onaverage 90 mol-% of vinyl end group (a+b 1.80).

Polymer III:

Analogous repetition of Example 1 with only 500 g of theα,ω-divinylpolydimethylsiloxane gives a polymer having a viscosity of214 mm²/s at 25° C. and an iodine number of 6.0. The product contains onaverage 86 mol-% of vinyl end groups (a+b=1.72).

Polymer IV:

30 g of 1,3-di(5-hexenyl)tetramethyldisiloxane are equilibrated with1350 g of a methyl-terminated polydimethylsiloxane having a mean chainlength of about 900 siloxy units with catalysis by phosphonitrilicchloride (100 ppm). Workup as in Example 1 gives a clear siloxanepolymer having a viscosity of 380 mm²/s at 25° C. and an iodine numberof 4.1. The polymer contains on average 83 mol-% of 5-hexenyl groups(a+b=1.66).

Polymer V:

600 g of a siloxane polymer of average composition (HMe₂SiO_(½))_(1,8)(Me₃SiO_(½))_(0.2) (Me₂SiO)₄₈ are mixed with 24 g of 1,5-hexadiene andthe mixture is heated to about 60° C. 15 mg of H₂PtCl₆H₂O (dissolved inabout 2 ml of isopropanol) are added, after which the internaltemperature rises by about 22° C. Volatile constituents are removed at130° C. and 3 hPa. The resulting product has a viscosity of 182 mm²/s at25° C. and an iodine number of 6.3. It contains 82 mol-% of 5-hexenylgroups (a+b=1.64).

Polymer VI:

Example 1 is repeated but now employing, instead of 100 g of themethyl-terminated polydimethylsiloxane, 86 g of a methyl-terminatedpolydimethylsiloxane having a viscosity of 20 mm²/s at 25° C. Workupgives a clear colourless polymer having a viscosity of 108 mm²/s at 25°C. and an iodine number of 7.9. The product (VI) contains on average 77mol-% of vinyl end groups (a+b=1.54).

Polymer VII:

250 g of an α,ω-divinylpolydimethylsiloxane with an average chain lengthof 29 siloxy units are equilibrated with 400 g of a methyl-terminatedpolydimethylsiloxane of viscosity 5000 mm²/s at 25° C. with catalysis by50 ppm of phosphonitrilic chloride at 145° C. Workup in accordance withExample 1 gives a clear polymer (VII) having a viscosity of 112 mm²/s at25° C. and an iodine number of 8.7. It contains on average 90 mol-% ofvinyl end groups (a+b=1.80).

Polymer VIII:

Example 7 is repeated with 500 g of a methyl-terminatedpolydimethylsiloxane having a viscosity of 1000 mm²/s at 25° C. ratherthan 5000 mm²/s. The viscosity of the product (VIII) is now 109 mm²/s at25° C. with an iodine number of 7.6. It contains on average 83 mol-% ofvinyl end groups (a+b=1.66).

Comparison Polymer 1:

Example 8 is repeated with 700 g of a methyl-terminatedpolydimethylsiloxane having a viscosity of 205 mm²/s at 25° C. insteadof the polymer with 5000 mm²/s. Equilibration and workup give a clearpolymer having a viscosity of 97 mm²/s at 25° C. and an iodine number of6.6. The product contains on average 55 mol-% of vinyl end groups permolecule (a+b=1.10).

Comparison Polymer 2:

=α,ω-divinylpolydimethylsiloxane having 98 siloxane units (=chain length98)

EXAMPLES 1 TO 3 AND COMPARATIVE EXPERIMENTS 1 AND 2

The following formulations (Table 1) are prepared from components A, B,C and D.

(A) alkenyl-functional siloxane: Polymer VI, VII, VIII or ComparisonPolymer 1 and 2

(B) H-siloxane crosslinker: polyhydridomethylsiloxane(methyl-terminated) containing 1.54% by weight of Si-bonded hydrogen

(C) catalyst: platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexdissolved in α,ω-divinylpolydimethylsiloxane (1% Pt content) (so-calledKarstedt catalyst in accordance with U.S. Pat. No. 3,775,452)

(D) Inhibitor: 1-ethynylcyclohexanol

The components are mixed in the sequence (A)+(D)+(B)+(C).

TABLE 1 Comparative Comparative Ex- Experiment Experiment ample 1 2 3 12 Polymer VII VIII VI Comparison Comparison Polymer 1 Polymer 2 (A) 100g 100 g 100 g 100 g 100 g (B) 4.5 g 3.9 g 4.0 g 3.4 g 3.6 g (C) 1.04 g1.04 g 1.04 g 1.04 g 1.04 g (D) 0.26 g 0.26 g 0.26 g 0.26 g 0.26 g mol-%90 83 77 55 100 of vinyl

The ratio of Si-bonded hydrogen to H₂C═CH groups is 2.0. Allformulations contain 0.25% of 1-ethynylcyclohexanol and have gel timesof >72 h.

The mixtures are knife-coated onto polyester film in a coat thickness ofabout 4 μm and are cured in a convection oven at 85° C. for 20 seconds.The results are summarized in Table 2.

TABLE 2 Release force Extract Release force [cN/cm] retention [% by wt.]A 7475 K 7476 T 154 [%] Example 1 5.9 18 11 9 >100 Example 2 11.6 16 88 >100 Example 3 6.5 16 9 8 >100 Comparative Silicone coating is softand tacky Experiment 1 Comparative 4.1 8 13 4 >100 Experiment 2

Extractable fractions are regarded as non-crosslinked constituents(extraction medium: methyl isobutyl ketone)

The release forces relative to the three Tesa adhesive tapes, and therelease force retention, were determined in accordance with FINAT 10 and11 printed in “Suppliers and Users Technical Manual”, June 1980, pages21 to 24, using customary commercial self-adhesive (pressure-sensitive)adhesive tapes 2.5 cm wide—“Tesafilm A 7475”, “Tesafilm K 7476” and“Tesafilm T 154” (from Beiersdorf A G, Hamburg, F R G; the “Tesa” partof the word is a registered trademark).

The comparison shows that an inadequate content of reactive alkenylgroups (<65 mol-%) in the linear organopolysiloxane (A) leads toinadequate curing (Comparative Experiment 1).

The quality of the substrate adhesion of the cured films is determinedrelative to a number of substrates in the abrasion test. To determinethe abrasion the coated substrates are clamped between thumb andforefinger. Then, with the finger of the other hand, rubbing with strongpressure is carried out a number of times rapidly backwards and forwardsover the taut substrate. If the adhesion of the silicone film to thesubstrate surface is poor, some of the silicone coating is abraded.Depending on its extent, the abrasion is evaluated using the ratings1-6, where a completely undamaged surface is given the rating 1 andcomplete abrasion is awarded the rating 6.

The results are summarized in Table 3.

TABLE 3 Comparative Compara- Experiment tive Ex- Example 1 2 3 2periment 1 Bosso 925 1 (1) 1 (1) 1 (1) 1-2 (1-2) 6 Cham 697 2-3 (2-3)1-2 (1-2) 1-2 (1-2) 3 (4-5) 6 Cham 699 1-2 (1-2) 1 (1-2) 1 (1) 2-3 (2-3)6 Polyester 1 (1) 1 (1) 1 (1) 1 (2-3) 6

Assessment of abrasion: immediate (after 5 days) Although ComparativeExperiment 2 also shows good curing, the formulations according to theinvention are considerably superior in abrasion behaviour.

EXAMPLE 4

MQ resin formulations are prepared at various concentrations from thefollowing components:

A₁ α,ω-divinyldimethylpolysiloxane comprising 1.2 mol ofvinyldimethylsiloxy, 0.8 mol of trimethylsiloxy and 27 mol ofdimethylsiloxy units, i.e. 60 mol-% of the end groups are vinyl groups(a+b=1.2).

A₂ MQ resin comprising (CH₃)₃SiO_(½) units (M₁), CH₂═CH(CH₃)₂SiO_(½)units (M₂) and SiO₂ units (Q), where the ratio of the sum of the unitsM₁+M₂ to the Q units is 0.7 and the ratio of M₁ units to M₂ units is1:7.3 (1400 g/C═C double bond).

CRA 1 CRA 2 A₁ 50 g 45 g A₂ 50 g 55 g iodine number 16.0 16.2 viscosity1200 mm²/s (25° C.) 6300 mm²/s (25° C.) mixed with: crosslinker B 10.2 g10.4 g catalyst C 1.1 g 1.1 g inhibitor D 0.1 g 0.1 g

B) H-siloxane comprising methylhydridosiloxane and trimethylsiloxaneunits with 15.4 g of Si-bonded hydrogen/kg

C) Platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (so-calledKarstedt catalyst in accordance with U.S. Pat. No. 3,775,452) dissolvedin α,ω-divinyldimethylpolysiloxane, having a viscosity of 1000 mm²/s at25° C. (1.0% Pt content)

D) 1-Ethynylcyclohexanol.

The freshly prepared, ready-to-use compositions contain 2.5 g ofSi-bonded hydrogen per mole of double bond. They are coated with a glassrod in a coat thickness of 4 μm onto a number of substrates and cured ina convection oven at 85° C. Then the abrasion behavior is tested.

The quality of the substrate adhesion of the cured films is determinedrelative to a number of substrates in the abrasion test. To determinethe abrasion the coated substrates are clamped between thumb andforefinger. Then, with the finger of the other hand, rubbing with strongpressure is carried out a number of times rapidly backwards and forwardsover the taut substrate. If the adhesion of the silicone film to thesubstrate surface is poor, some of the silicone coating is abraded.Depending on its extent, the abrasion is evaluated using the ratings1-6, where a completely undamaged surface is given the rating 1 andcomplete abrasion is awarded the rating 6.

The results are summarized in Tables 4 and 5.

TABLE 4 Abrasion test, Abrasion test, immediate 2 weeks 20 seconds/85°C.: CRA 1 CRA 2 CRA 1 CRA 2 Paper 925 1 1 1 1 (from BOSSO) HDPE filmQ24000 1 1 1 1 (from 4P Folie) Polyester film 1 1 1 1 (from Hoechst)

TABLE 5 Abrasion test, Abrasion test, immediate 2 weeks 30 seconds/85°C.: CRA 1 CRA 2 CRA 1 CRA 2 Paper Algrosol 1 1 1 1 1 Paper 697 - 125g/m² 1 1 1 1 (from Cham) Paper 699 - 125 g/m² 1 1 1 1 (from Cham)

1=no abrasion−6=complete abrasion

The coatings adhere perfectly to all substrates.

COMPARATIVE EXPERIMENT 3

A commercial resin formulation (CRA 17 obtainable from Wacker-ChemieGmbH) is mixed 1:1 with an α,ω-divinyldimethylpolysiloxane having aviscosity of 180 mm²/s at 25° C. and the mixture is blended withcrosslinker (B) to an equal SiH/C═C ratio as described in Example 4.Components (C) and (D) are added in exactly the same concentrations asdescribed in Example 4.

The freshly prepared composition is coated with a glass rod in a coatthickness of 4 μm onto a number of substrates and cured in a convectionoven at 85° C. The substrate adhesion is determined in the abrasion testas described in Example 4. The results are summarized in Tables 6 and 7.

TABLE 6 Abrasion test 20 seconds/85° C. immediate after 2 weeks Paper925 1 1-2 (from Bosso) HDPE film Q2400 1 4-5 (from 4P Folie) Polyesterfilm 5 5 (from Hoechst)

TABLE 6 Abrasion test 20 seconds/85° C. immediate after 2 weeks Paper925 1 1-2 (from Bosso) HDPE film Q2400 1 4-5 (from 4P Folie) Polyesterfilm 5 5 (from Hoechst)

In almost all cases the substrate adhesion is very poor and the coatingis unusable.

What is claimed is:
 1. A crosslinkable composition comprising: (A₁)linear organopolysiloxanes containing aliphatically unsaturatedhydrocarbon radicals, of the general formula R¹_(a)R_(3-a)SiO(R₂SiO)_(c)[R₂Si—Y—SiR₂O(R₂SiO)_(c)]_(d)SiR_(3-b)R¹_(b)  (I) where each R independently is identical or different and is amonovalent, unsubstituted or halogenated hydrocarbon radical which hasfrom 1 to 18 carbon atoms per radical and is free from terminalaliphatic carbon—carbon multiple bonds, R¹ is a monovalent aliphaticallyunsaturated hydrocarbon radical having from 2 to 14 carbon atoms perradical, Y is a divalent organic radical which is free from terminalaliphatic carbon—carbon multiple bonds, a is 0 or 1, b is 0 or 1, andthe sum a+b per molecule is 1 or 2, c is an integer from 1 to 1000 and dis 0 or an integer from 1 to 10, with the proviso that without the useof MQ silicone resins (A₂) the sum a+b in formula (I) is on average from1.3 to 1.9, and that with the use of MQ silicone resins (A₂) the sum a+bin formula (I) is on average from 1.0 to 1.9.
 2. The crosslinkablecomposition of claim 1, wherein R¹ is a vinyl radical.
 3. Thecrosslinkable composition of claim 1, wherein d is
 0. 4. Thecrosslinkable composition of claim 2, wherein d is
 0. 5. Thecrosslinkable composition of claim 1, wherein said MQ silicone resins(A₂) comprise units of the general formula R₃SiO_(½)(IV), R¹R₂SiO_(½)(V) and SiO₂ (VI), where R and R¹ have the meaning previously indicated,and the ratio of M units of the formulae (IV) and (V) to Q units of theformula (VI) is from 0.5 to 1.5 and the ratio of saturated M units ofthe formula (IV) to unsaturated M units of the formula (V) is from 5 to20.
 6. The crosslinkable composition of claim 2, wherein said MQsilicone resins (A₂) comprise units of the general formula R₃SiO_(½)(IV), R¹R₂SiO_(½) (V) and SiO₂ (VI), where R has the meaning previouslyindicated, wherein R¹ is vinyl, and the ratio of M units of the formulae(IV) and (V) to Q units of the formula (VI) is from 0.5 to 1.5 and theratio of saturated M units of the formula (IV) to unsaturated M units ofthe formula (V) is from 5 to
 20. 7. The crosslinkable composition ofclaim 3, wherein said MQ silicone resins (A₂) comprise units of thegeneral formula R₃SiO_(½) (IV), R¹R₂SiO_(½) (V) and SiO₂ (VI), where Rhas the meaning previously indicated, R¹ is a monovalent aliphaticallyunsaturated hydrocarbon radical having from 2 to 14 carbon atoms perradical, and the ratio of M units of the formulae (IV) and (V) to Qunits of the formula (VI) is from 0.5 to 1.5 and the ratio of saturatedM units of the formula (IV) to unsaturated M units of the formula (V) isfrom 5 to
 20. 8. The crosslinkable composition of claim 4, wherein saidMQ silicone resins (A₂) comprise units of the general formula R₃SiO_(½)(IV), R¹R₂SiO_(½) (V) and SiO₂ (VI), where R and R¹ have the meaningpreviously indicated, and the ratio of M units of the formulae (IV) and(V) to Q units of the formula (VI) is from 0.5 to 1.5 and the ratio ofsaturated M units of the formula (IV) to unsaturated M units of theformula (V) is from 5 to
 20. 9. A process for producing coatings whichrepel tacky substances, said process comprising applying thecrosslinkable compositions of claim 1 to the surfaces which are to bemade repellent to tacky substances, and curing the crosslinkablecomposition.
 10. A process for producing coatings which repel tackysubstances, said process comprising applying the crosslinkablecompositions of claim 2 to the surfaces which are to be made repellentto tacky substances, and curing the crosslinkable composition.
 11. Aprocess for producing coatings which repel tacky substances, saidprocess comprising applying the crosslinkable compositions of claim 3 tothe surfaces which are to be made repellent to tacky substances, andcuring the crosslinkable composition.
 12. A process for producingcoatings which repel tacky substances, said process comprising applyingthe crosslinkable compositions of claim 4 to the surfaces which are tobe made repellent to tacky substances, and curing the crosslinkablecomposition.
 13. A process for producing coatings which repel tackysubstances, said process comprising applying the crosslinkablecompositions of claim 5 to the surfaces which are to be made repellentto tacky substances, and curing the crosslinkable composition.
 14. Aprocess for producing coatings which repel tacky substances, saidprocess comprising applying the crosslinkable compositions of claim 6 tothe surfaces which are to be made repellent to tacky substances, andcuring the crosslinkable composition.
 15. A process for producingcoatings which repel tacky substances, said process comprising applyingthe crosslinkable compositions of claim 7 to the surfaces which are tobe made repellent to tacky substances, and curing the crosslinkablecomposition.
 16. A process for producing coatings which repel tackysubstances, said process comprising applying the crosslinkablecompositions of claim 8 to the surfaces which are to be made repellentto tacky substances, and curing the crosslinkable composition.